Hi everyone. I have a Telefunken 2430 valve receiver which has given me much listening pleasure over the years. It went into storage for a time after a house move; after I unpacked it, it was working fine but I noticed it had collected quite a bit of dust/dirt and used an air duster to clean it -- big mistake because after that I had a persistent and annoying hum from both channels. After much cleaning and replacing of valves, the problem persists; however, after the last attempt at trouble-shooting, a resistor on the amplifier board burned out. Because of the way it's burned up, the colour coding is gone - it's placed below an ECC83 valve.

I was wondering if anyone could help me identify this resistor so I can replace it. I haven't switched it on since. I know very little about electronics and have basic soldering skills. There are no specialist hi-fi shops near me. I have attached a photo:

Thanks for any help. I'd really like to salvage this if I can. Is this resistor really fried, or can I take a chance on switching it on?

Hi Frank, thanks for your reply. There are four electrolytic caps beneath the output transformer - I've noticed that they seem to be quite leaky as they're old paper caps - the problem with that is that the paper is so faded I can't read the values. Thankfully I do have the spec sheet on PDF. Also those caps are very hard to get at because of the way the amp is constructed - quite a lot of disassembly and wire-cutting - I better take a lot of photos before I start.

Hi Michael, thanks very much for taking the time to get that information for me. Yes, the part of the board is at the very bottom left, below the lower ECC83 valve near the edge of the board. The other thing I wanted to ask is - is there a specific wattage for that resistor?

I'm sorry to hear it means there's a serious problem as my experience of electronics is very limited. I will have to ask around and see if I can find someone more qualified than myself to measure the voltages.

My original plan was to replace the resistor and if it worked, all well and good; if not, to seek other help. I love this receiver so much that I'm willing to work at it.

Many thanks - if you have any further ideas or information, they will be gratefully received, and I will keep this thread updated on my progress.

The other thing I wanted to ask is - is there a specific wattage for that resistor?

Hello numinous

Please have a look at the schematic diagramm on the first half of the ECC83. There has to be 120V on the Anode and 1V on the Kathode measured against Ground. The resistor from Kathode to ground determines the current, that flows through the tube.

I=U / R so 1V / 2200Ohm = 0,00045A = 0,45mA

And that is exactly the value from the schematic printed on top of the tube-symbol. Power rating is:

P=U x I so 1V x 0,00045A = 0,00045W

So every resistor with the normal power rating of 1/4W or 1/2W is good enough.

And now you can see yourself that something goes really wrong there, because you need way more current through the resistor to burn it down.